Age: There has been a continuous presence of a lake in the area for approximately one million years, since the formation of Lake Biwa's predecessor, Lake Katata. Lake Katata gradually moved to the west to the present position of the southern basin of Lake Biwa, and then expanded north-east, forming the current north basin about 400 000 years ago.

However, to the south east of Lake Biwa there were four other lakes that existed back to about four million years ago. Due to its age, Lake Biwa is classified as one of the world's few 'ancient' lakes.

Uses:

Supplies 14 million people with drinking water (including the cities of Osaka and Kyoto).